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SunPower solar panels: the complete review

SunPower solar panels are one of the most frequently requested solar panel brands on the EnergySage Marketplace and for a good reason: SunPower panels are often the most efficient (read: powerful!) products on the market today, and they offer an industry-leading warranty. For many years, SunPower has been a fully-integrated solar shop, manufacturing solar cells and panels and then offering sales and installation services for residential and commercial applications. But, while they are considered some of the best panels, they do come at a premium price.

When evaluating your solar panel options, it’s essential to compare what’s available so you can be confident in your solar investment. Let’s look at SunPower’s solar panel technology and how it compares to other leading solar panel brands available today.

This is an unbiased review: EnergySage is not paid to review brands or products, nor do we earn money from affiliate advertising in this article. The content of this blog is based on research and information available at the time of writing. Learn more about our mission and how we make money as a company.

Key takeaways

  1. SunPower solar panels range in efficiency from 21.7% to 22.8% and they have 25-year workmanship and performance warranties.

  2. SunPower solar panels cost between $3.48 and $4.10 per Watt on the EnergySage Marketplace – that’s $20,880 to $24,600 for a 6 kW system before the federal solar tax credit.

  3. In 2019, SunPower spun off the manufacturing arm of its business into Maxeon Solar Technologies – however, as of 2023, Maxeon only manufactures some of SunPower’s solar panels.

  4. Shop for SunPower solar panels (and many other brands!) today on the EnergySage Marketplace.

What’s in this article?

SunPower solar panels: what series are available?

If you’re interested in SunPower solar panels, you can choose from three different series: the M Series, X Series, and U Series. Here’s what you need to know about each of them:

M Series

The SunPower M Series are currently manufactured by Maxeon Solar Technologies, which took over SunPower’s manufacturing arm in 2019. This series offers the highest output (aka wattage) and most efficient panels in SunPower’s lineup (but they do come with a premium price tag as well). The M Series comes with five output options: 420 Watts (W), 425W, 430W, 435W, and 440W.

All of SunPower’s Maxeon-produced solar panels are made up of n-type, monocrystalline, half-cut solar cells – aka the building blocks of solar panels. N-type solar cells are made up of two silicon layers and are more expensive to produce than p-type cells, which is why you may come across more panels with p-type cells. The half-cut cell structure of n-type solar cells reduces heat loss because the cells themselves are smaller, making them much more efficient than conventional panels, meaning you can often install fewer panels on your roof.

X Series

SunPower’s X Series are also manufactured by Maxeon. Compared to the M Series, they are lower in output but tend to cost slightly less, so they’re a good fit for many solar shoppers. The X Series comes with two output options: 360W and 370W.

U Series

Considered their “budget” series, the U Series is SunPower’s most recent addition to their lineup – and frankly, there’s still a lot that’s unknown about them. These panels are not manufactured by Maxeon; instead, they’re manufactured by a few different solar companies, including Aptos Solar Technology, a U.S.-based solar manufacturer, and potentially Waaree, a large India-based solar manufacturer (though Waaree is unconfirmed as of March 2023). Overall, this means that the U Series performance metrics are currently unclear, but we will continue to update this article as more definitive information arises.

We’ll dive into the efficiency ratings, performance, and warranties of M Series and X Series panels below.

How do SunPower solar panels compare

There are four key metrics that you should review as you evaluate solar panel quality and determine the best solar panels for you: efficiency, performance, warranty, and price. We’ll explain what each of these means and why they’re important – and show how SunPower solar panels stack up against each other and other leading brands in the solar industry.


The term “solar panel efficiency” or “conversion efficiency” refers to how well a solar panel captures sunlight and converts it into usable photovoltaic electricity. In the same conditions, a high-efficiency solar panel will produce more electricity than a lower-efficiency panel of the same size. So, if you’re choosing between panels, ones with higher efficiency ratings are generally preferable.

The efficiency of your SunPower solar panels will vary depending on the specific model you choose for your system. SunPower panel efficiency ranges from 21.7% to 22.8% (excluding the U Series), making them some of the most efficient solar panels currently available. SunPower claims the top spot on the EnergySage Marketplace regarding panel efficiency, with its M Series 440W panels boasting the highest efficiency rating of any home solar panel on the Marketplace.

SunPower panel series efficiency SunPower panel seriesEfficiency rating SunPower M Series 420W21.7% SunPower M Series 425W22% SunPower M Series 430W22.3% SunPower M Series 435W22.5% SunPower M Series 440W22.8% SunPower X Series 360W22.1% SunPower X Series 370W22.7% SunPower U SeriesNot disclosed

Performance (temperature coefficient)

Temperature coefficient is an indicator of how well your solar panels perform in less-than-ideal conditions. Solar panels, like other electronic equipment, perform better when kept cool (ideally around 25°C/77°F). The temperature coefficient tells you how much your panel’s performance will change during hot, sunny summer days.

For every degree above 25°C (77°F), your solar panel’s electricity production will decrease by its temperature coefficient. The temperature coefficient of all of the SunPower M Series and X Series panels is -0.29%/°C. This means that if the panel’s temperature increases by one degree from 25°C (77°F), its electricity production will decrease by 0.29%; if its temperature rises to 35°C (95°F), electricity production will reduce by 2.9% 

Your solar panels will likely see more than a few hot and sunny days each year, so ideally, they will have the lowest temperature coefficient possible. SunPower’s solar panels have lower temperature coefficients as far as the industry goes at -0.29 for all their series (except the U Series, which is unknown). For comparison, the most popular brand of solar panels on EnergySage, Q CELLS, offers panels with a temperature coefficient of -0.34, while Panasonic panels all have a temperature coefficient of -0.26.

Sunpower panel series temperature coefficient SunPower panel seriesTemperature coefficient SunPower M Series 420W-0.29%/°C SunPower M Series 425W-0.29%/°C SunPower M Series 430W-0.29%/°C SunPower M Series 435W-0.29%/°C SunPower M Series 440W-0.29%/°C SunPower X Series 360W-0.29%/°C SunPower X Series 370W-0.29%/°C SunPower U SeriesNot disclosed


Whether you’re buying a TV, a car, or solar panels, the brand should stand behind their product with a strong warranty. A solar panel’s materials warranty (sometimes referred to as the product or equipment warranty) is a guarantee from the company that they will replace your panel if it fails due to manufacturing defects or environmental issues.

SunPower offers a 25-year warranty, guaranteeing that their panels will still produce at least 92% of their original output by the end of the warranty term. This warranty applies even if the panels are not registered and they offer a 40-year warranty for panels that are registered within six months of installation and installed by a SunPower-certified installer. This 40-year warranty offering is the best warranty term in the industry, showing SunPower’s commitment to its panels’ durability and guaranteeing that SunPower solar modules will still be generating 88.25% of their minimum peak power output at year 40.

As with most warranties, SunPower’s warranty covers degradation of the panel quality but not any corrosion from elements like salt water. You can see the degradation warranty coverage of all of SunPower’s panels in the table below.

SunPower panel power output warranty SunPower panel seriesAnnual degradation (%)Power at year 25 (%)Power at year 40 (%) SunPower M Series 420W0.25%92%88.25% SunPower M Series 425W0.25%92%88.25% SunPower M Series 430W0.25%92%88.25% SunPower M Series 435W0.25%92%88.25% SunPower M Series 440W0.25%92%88.25% SunPower X Series 360W0.25%92%88.25% SunPower X Series 370W0.25%92%88.25% SunPower U SeriesNot disclosedNot disclosedNot disclosed

For more information, check out our in-depth review of SunPower’s warranty and our guide to comparing the solar panel warranties of the top brands on the market.

How much do SunPower solar panels cost?

For many homeowners, the final decision around the solar power equipment they choose rests on cost. The total price you’ll pay for a solar energy system with SunPower panels will vary depending on the other equipment (such as inverters and mounts) used in the installation, as well as the characteristics of your roof.

To identify the range of prices for SunPower systems, we analyzed quotes that homeowners received from installers on the EnergySage Marketplace that included SunPower solar panels. Most SunPower systems are typically priced between $3.48 and $4.10 per watt – distinctly on the pricier end of residential solar panels quoted on the EnergySage Marketplace.

This means that, for a 6 kW system, your gross cost (before subtracting any tax credits or other incentives) would be anywhere from $20,880 to $24,600 – this is the highest average price range we see on the EnergySage Marketplace. As a point of comparison, the cost of a 6 kW system from Tesla ranges from $18,180 to $20,100. But, most homeowners pay much less than the total gross cost; there are plenty of solar incentives and rebates to help you reduce upfront costs, including the 30% federal tax credit for solar, which lowers the cost range of a SunPower solar panel system to $14,616 to $18,220.

Advantages & disadvantages of SunPower solar panels

As with any product that is such a significant investment, SunPower panels have advantages and disadvantages to keep in mind before deciding to make a purchase. Whether your primary motivation for switching to solar is sustainability or lowering your electric bills, it’s important to weigh your options.

Pros of SunPower solar panels

  1. Superior product warranty: SunPower solar panels come with one of the most extended and comprehensive warranties available at 25 years, in addition to the 40-year, 88.25% warranty available if you register your panels.

  2. Excellent efficiency: SunPower solar panels are the most efficient solar panels currently available on the EnergySage Marketplace.

  3. Battery system compatibility: in addition to solar panels, SunPower offers the SunVault Storage system, allowing you to install a completely integrated system under one company.

Cons of SunPower solar panels

  1. Cost: SunPower solar panels are some of the most expensive panels on the market, making some of the less expensive (if somewhat lower quality) options more enticing for those concerned about costs.

  2. Manufacturing: though this isn’t a direct disadvantage, SunPower no longer manufactures their own panels. It’s still unclear exactly what companies are manufacturing their U Series and very little information is available about these panels.

How to find the best price on SunPower solar panels

The best way to determine whether SunPower solar panels are the best solar solution for your home is to review multiple quotes with different solar equipment before making a decision. On the EnergySage Marketplace, you’ll receive quotes from our network of qualified, vetted solar installers so you can go solar with confidence. If you’re already set on certain equipment – SunPower or otherwise – simply note your preference in your profile so installers can include it in your quotes.

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